This invention relates generally to a compact and simplified system for operating and digitally controlling several functions in a camera, especially cameras of the instant-developing type having film advancing and spreading functions.
Photographic apparatus of the instant-developing type expose and process automatically film units of the self-developing kind. Normally, a plurality of these unexposed units are housed in a stacked array in a film pack located adjacent a pair of pressure applying rollers in the camera body.
Once the film pack is loaded in the camera, the user frames the subject to be photographed, focuses the optical system and presses a button to initiate a cycle of camera operation. The operating cycle includes the step of exposing the uppermost one of the stacked film units under the control of a light-sensing exposure control circuit. Following exposure, the film unit is advanced to the pressure-applying rollers, which are mounted adjacent a camera body exit slot. For advancing the uppermost film unit from the pack after exposure there is provided a film advance pick arrangement. The pick is operable to advance the film unit through a film pack exit slot and into engagement with the rollers. Thereafter, the film is advanced by the rollers, while the latter progressively causes uniform spreading of the processing composition in the film unit. The film unit is also partially ejected from the camera body. Thereafter, the camera mechanisms are reset for the next cycle of camera operation.
There are several known systems for initiating and controlling one or more or all of the above functions. These systems include a battery operated motor which, through a plurality of gears forming a gear train, drives a timing or sequencing wheel, gear or cam. For example, this sequencing wheel cooperates with a spring biased-pick arrangement for allowing the latter to pick the topmost unit from the pack and into engagement with the pressure applying rollers. Also, the sequencing wheel cooperates with the plurality of gears for driving the pressure-applying rollers so as to spread the fluid and advance the unit. Examples of such systems are disclosed in commonly assigned U.S. Pat. Nos.: 3,753,392, 3,943,786 and 4,047,192.
The foregoing systems work quite satisfactorily. However, they require a multiplicity of components. Consequently they are relatively complicated and costly to manufacture, and assemble. As is appreciated readily, increased costs are significant in the highly competitive photographic field. Moreover, such systems generally require relatively significant drains on battery power during a photographic cycle.
Attempts for simplifying the construction and operation of the foregoing kinds of sequencing systems have been undertaken. One is described in commonly assigned U.S. Pat. No. 3,889,280. Included in such a system is a battery powered motor which drives a timing belt. The timing belt drives an intermediary gear which drives the processing rollers. Also, the timing belt controls a cam that operates a mirror and then operates a film picking arrangement. Because several gears have been eliminated less power of the battery is consumed. Also this system requires the motor to be behind the film pack. Thus miniaturization is somewhat impeded. However, with such a motor there is no indexing or stepping of the belt. Hence, with such a system there is a tendency for lack of precision in sequencing. Towards that end the patent discloses the need for special circuitry for minimizing the problem of the motor causing overshooting of the belt and its associated cam member.